Motor vehicles with different drive systems, include propulsion by means of an internal combustion engine, an electric motor, or a combination of the two motor types. In motor vehicles with a combination of internal combustion engine and electric motor drive system, one distinguishes between motor vehicles with a pure hybrid drive, also known as “Plug-in hybrid electric vehicle” (PHEV), and “Range Extenders”.
PHEV vehicles can have electric, electric/combustion, and also combustion engine propulsion. The range of the vehicle with pure electric drive is around 50 km. Vehicles with “Range Extenders” are driven constantly by electric propulsion. The battery of the vehicle is charged during travel by a generator driven by the combustion engine.
A PHEV and a vehicle with “Range Extender” are motor vehicles whose battery can be charged additionally by an external power network or charging system.
The air conditioning of the passenger compartment of electric vehicles, makes use of either electric resistance heaters (PTC) or heat pump systems, since the waste heat of the electric motor is not enough to heat the passenger compartment. PTC heating systems are economical in manufacture, but due to the consumption of electrical energy they reduce the operating range of the electric vehicle. The use of heat pump systems is more cost-intensive, but the impact on the operating range of the electric vehicle is less.
In motor vehicles with a combination drive unit of combustion engine and electric motor, the use of a PTC heating system or heat pump system likewise reduces the range of the electric motor, but the travel can continue due to the operation of the combustion engine. Furthermore, the operation of the combustion engine provides heat for the heating of the passenger compartment to a higher temperature level. Moreover, the heat provided by modern internal combustion engines is not enough to heat the passenger compartment adequately. An important aspect of motor vehicles with “Range Extender” is that the combustion engine is operated at the optimal point and the available heating power is low.
Due to the heating by a PTC heating system or a fuel-operated supplemental heater, the passenger compartment can be comfortably heated and preconditioned. Still, the use of these systems in motor vehicles with electric motor drive or with hybrid drive is questionable for ecological reasons.
Air conditioning systems of motor vehicles with heating function may have a refrigerant circuit with a supplemental heat exchanger operating as an evaporator. The supplemental heat exchanger is usually configured as a connection to a coolant circuit, serving to control the temperature of components of the drive unit in motor vehicles with electric motor drive. In motor vehicles with internal combustion engine, the supplemental evaporator is used to provide an option for heat transfer between the cooling circuit of the combustion engine and the refrigerant circuit.
For example, a system for a motor vehicle for the heating and/or cooling of a passenger compartment and for cooling an internal combustion engine is found in DE 10 2010 038 406 A1. The system comprises a coolant circuit for cooling an internal combustion engine with an ambient air heat exchanger to surrender heat from the coolant to the ambient air and a refrigerant circuit with a condenser, a compressor, and a first evaporator, exposed to a flow of air from the passenger compartment, for cooling the passenger compartment in the cooling mode. In the heat pump mode, the air being taken to the passenger compartment can be heated by the refrigerant circuit, taking up heat from the ambient air. The refrigerant circuit in this case has a second evaporator and condenser, which are configured as coolant heat exchangers. The refrigerant circuit is thus thermally coupled to the coolant circuit.
In DE 10 2009 060 860 A1 an air conditioning system is described for an electric or hybrid vehicle with a refrigerant circuit and a temperature control circuit for controlling the temperature of the passenger compartment and a vehicle component. The circuits are thermally coupled via a heat exchanger for taking up heat from the temperature control circuit and a heat exchanger for surrendering heat to the temperature control circuit. When controlling the temperature of vehicle components, heat from the temperature control circuit is transferred to the refrigerant circuit at the low pressure side and heat from the refrigerant circuit is transferred to the temperature control circuit at the high pressure side of the refrigerant circuit.
With the help of the two supplemental heat exchangers in the refrigerant circuit as thermal couplings to the temperature control circuit, consumption devices such as the periphery of the electric motor, especially the battery, fuel cells, power electronics and/or the passenger compartment are conditioned and climate-controlled in this way. Thanks to a separation of the temperature control circuit into two independent circuits, the internal combustion engine can also be cooled, besides the mentioned components. The heat given off by the combustion engine is transferred to the surroundings or used to heat the air going to the passenger compartment.
Furthermore, the power from the operation of photovoltaic cells or solar panels can also be incorporated in the corresponding circuits, for example.